Motivation for this change

https://github.com/lxqt/lxqt/releases/tag/0.15.0

• lxqt: format nix expressions with nixpkgs-fmt
• lxqt: add update script tailored to LXQt packages
• lxqt: add updater script to individual packages
• lxqt: remove old update script
• lxqt.compton-conf: 0.14.1 -> 0.15.0
• lxqt.libfm-qt: 2019-09-22 -> 0.15.0
• lxqt.liblxqt: 0.14.1 -> 0.15.0
• lxqt.libqtxdg: 3.4.0 -> 3.5.0
• lxqt.libsysstat: 0.4.2 -> 0.4.3
• lxqt.lximage-qt: 0.14.1 -> 0.15.0
• lxqt.lxqt-about: 0.14.1 -> 0.15.0
• lxqt.lxqt-admin: 0.14.1 -> 0.15.0
• lxqt.lxqt-archiver: 2019-09-25 -> 0.1.1
• lxqt.lxqt-build-tools: 0.6.0 -> 0.7.0
• lxqt.lxqt-config: 0.14.1 -> 0.15.0
• lxqt.lxqt-globalkeys: 0.14.3 -> 0.15.0
• lxqt.lxqt-notificationd: 0.14.1 -> 0.15.0
• lxqt.lxqt-openssh-askpass: 0.14.1 -> 0.15.0
• lxqt.lxqt-panel: 0.14.1 -> 0.15.0
• lxqt.lxqt-policykit: 0.14.1 -> 0.15.0
• lxqt.lxqt-powermanagement: 0.14.1 -> 0.15.0
• lxqt.lxqt-qtplugin: 0.14.0 -> 0.15.0
• lxqt.lxqt-runner: 0.14.1 -> 0.15.0
• lxqt.lxqt-session: 0.14.1 -> 0.15.0
• lxqt.lxqt-sudo: 0.14.1 -> 0.15.0
• lxqt.lxqt-themes: 0.14.0 -> 0.15.0
• lxqt.obconf-qt: 0.14.1 -> 0.15.0
• lxqt.pavucontrol-qt: 0.14.1 -> 0.15.0
• lxqt.pcmanfm-qt: 0.14.1 -> 0.15.0
• lxqt.qlipper: 5.1.1 -> 5.1.2
• lxqt.qps: 2.0.0 -> 2.1.0
• lxqt.qterminal: 0.14.1 -> 0.15.0
• lxqt.qtermwidget: 0.14.1 -> 0.15.0
• lxqt.screengrab: 2.0.0 -> 2.0.1

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.